Furnace will not start at all; no lights, no blower, no inducer operation.

Safety first: Use caution when working around electrical panels.

• Check breaker: Locate the furnace breaker in the electrical panel and ensure it is ON. If tripped, reset once. If it trips again, call a professional.
• Service switch: Verify the furnace service switch (often looks like a light switch near the unit) is ON.
• Door switch: Ensure the blower compartment door is properly installed and depressing the door switch.
• Control board fuse: With power OFF, inspect and replace the low-voltage fuse on the control board if blown.

If the furnace still shows no signs of life, the transformer or control board may be failed and should be tested by a technician.